Control needle for a spray device



Nov. 19, 1963 c. KE LFGREN 3,111,271

CONTROL NEEDLE FoR A SPRAY DEVICE Fld June 2, 1960 FIG. 2

United States Patent Office 3,111,271 Patented Nov. 19, 1963 3,111,271 CGNTRQL NEEDLE FR A SPRAY DEVICE Carl ke Lfgren, Hagersten, Sweden, assignor to Svenska Maskinaktiebolaget Greilf, Stockholm, Sweden, a Swedish joint-stock company Filed `lune 2, 1960, Ser. No. 33,417 Claims priority, application Sweden .lune 11, 1959 2 Claims. (Cl. 239-468) This invention relates to control needles for spray devices -and, more particularly, to control needles for paint spray guns.

In paint spray guns, the needle which closes and opens the paint outlet of the spray tip is conventionally made of a metal such 'as steel. The use of steel is very disadvantageous inasmuch as the abrasive action of the paint will alter the shape of lthe needle so that the needle subsequen-tly cannot close the outlet the shape of which is also altered and thus the gain will leak.

I have Ifound ythat the substitution yof a plastic material in place of metal Afor forming needles of lthe above indicated type is not satisfactory. Thu-s, for example, certain types of paint can soften these plastic materials so that they cannot withstand pressure, thus enabling the needle to bend so that the closing of the paint outlet by the needle is less `eli'ioient because the `tip of `a. plastic needle enters the associated iiuid outlet at a slight angle whereby the needle does not completely close the outlet so that leakage is possible.

It is an object of the invention to provide lan improved needle and thereby an improved spray device and paint spray gun which avoids the diiculties noted above, these diliiculties being inherent in the use of needles made entirely from metal or entirely from plastic.

To achieve this object, I employ la needle which is partly of a rigid material lSuch as metal and partly of a plastic material such as nylon. The plastic material is employed as the tip of the needle iand is that portion of the needle which enters the spray outlet. The rigid material provides the necessary strength and control.

Other objects of this invention, as well las features and advantages thereof, will be apparent from the following detailed description as illustrated in the accompanying drawings, in which:

FIG. l illustrates a paint spray gun partially in section and embodying 'a needle control provided in accordance with the invention;

FIG. 2 illustrates, partially broken away and partially in section, the spray outlet, as well as the associated needle tip provided in accordance with the invention; and

FIG. 3 is `a cross-sectional view of the structure of FIG. 2 taken along line III-IH.

In FIG. l is illustrated a pain-t spray gun comprising a handle 12, a trigger 14, an adapter y16 for connection to ya source of paint, an adapter 18 for connection to a source of a pressure medium such as compressed air, a barrel or -body 20 having an elongated chamber C and adjustment knobs 22 and 24.

At one end .of the barrel 20 is a substantially cylindrical spray outlet opening 26 surrounding Iwhich is an annular orice `2S through which flows the compressed air. This compressed air in conventional manner aspirates the paint in the form of a spray via spray outlet opening 26, the flow of the paint from adapter 16 through discharge opening 26 being controlled and obturated by means of control needle 30, ywhich is under the control of trigger 14 and is supported in =a bushing or bearing 31. It will be noted that a needle made 'entirely from nylon would Wear at bushing 31 and cause the gun to leak.

FIG. Z illustrates spray outlet opening 26 in a greater detail and, as can be seen, there is included an outermost cylindrical portion 32 into which opens an inner conical portion or seat 34. For purposes of manufacturing and facilitating paint flow, there is also provided a further conical portion 36.

Needle 30 consists of -two sections, to yWit, rigid elongated stem section 38 which is a rigid direotioncontrolling force-transmitting rod rnade of unetal such as, for .example, stainless steel and a section 40 which is a yieldable resilient section of paint resistant plastic such as, for example, nylon.

In an ideal spray gun, needle 30 and -opening 26 have perfectly circular cross-sections and are perfectly aligned in an axial sense. Under such conditions, the use of a needle made entirely of metal might be possible, 'although even in this case, the abrasive action of the substance to be sprayed would soon destroy the ability of these components to mate. FIG. 2, however, illustrates the usual situation in which the tolerances of manufacture displace Athe needle 30 from a true axial alignment with the passage 26 and, in this instance, the needle 30 can be seen striking the edge of the passage 26 as indicated at 42.

The passage or opening 26 is conveniently given a configuration as illustrated in FIG. 2 whereby it comprises a cylindrical portion 32 land a conical portion 34. The tip of needle 30 is also lgiven this configuration so that section 49 includes `a cylindrical portion 44 adapted to cleanse residue materials from cylindrical portion 32, as well as a conical portion 46. The cylindrical 'and conical portions of both the outlet 26 and resilient section 4d are, respectively, concentric or coaxial and contiguous. With reference to deformable portion 4l), conical portion 46 tapers into cylindrical portion 44 (which itself terminates in -a conical portion 48 for purposes of manufacture). The tip, it will be noted, -in order to be somewhat flexible is of an axial length substantially greater than its diameter or transverse dimension -and extends as a solid mass for a substantial distance (e.g., at least twice its diameter) from lthe end of stem 38.

The sections 33 :and 46 of needle 36 are provided with mating male and female members. Preferably, portion 38 is provided with an extension or anchoring device 50 having a head 52 or some other irregular projection which is 'accommodated in a socket 54 provided in resilient section 49. Preferably, as a matter of manufacturing procedure, the tip 4i) is molded directly on the rigid section 38.

It is to be noted, in connection with the manufacture of a control needle provided in accord-ance with the invention, that 4the mold form fo-r the tip can be made so as to correspond directly with the desired final shape of the tip. Therefore, after molding, the needle is ready for use and requires no machining.

FIG. 3 indicates by dotted lines the shape of outlet 26 and, particularly, :of cylindrical portion 32 thereof following the abrasive action of the substance to be sprayed. It will be noted how this abrasive elf-ect changes .the circular hole to an oval shape to which only a plastic tip can conform.

In conclusion, it is noted that the comparatively large tolerances required for the manufacture of spray devices, as Well Eas the abrasive action of the substance to be sprayed, has the unfortunate result that a control needle for a spray `outlet will rarely, if ever, be concentric with the latter. It will, therefore, be impossible for the control needle to operate effectively and efciently unless this needle is provided as contemplated by the invention. The invention contemplates the providing of a deformable tip which facilitates the conformance of this tip 'with the shape of Ian associated outlet and, at the same time, the invention contemplates preserving sufficient strength in fthe needle by the use of a rigid section made of, for example, metal. More particularly, in the preferred embodiment -of the invention where the tip is of nylon (which is substantially -inertt with respect to paint) and the major portion of the body is of steel, the tip of nylon is about one-tenth of the overall length of the needle. It is to be noted that nylon, which is conventionally employed for bearings, inherently provides Ia friction-free surface on the tip which inures to the benefit of the invention.

There Will now be obvious to those skilled in the art many modifications and variations of the structure set forth above. These modications and variations Iwill not, however, depart from the scope rof the invention ir they are dened by the following claims.

What is claimed is:

1. A paint spray device comprising a body provided with an elongated chamber fora fluid 'to be sprayed, said body including a substantially conical seat at an end of said chamber and being provided with a substantially cylindrical opening connected to `and concentric with lsaid seat and through Which said fluid leaves said chamber; a needle extending through said chamber and including an elongated rigid stem including an irregular end portion and a tip on said stem and engaging sa-id irregular end portion, the engagement between said tip `and irregular yend portion preventing rotational displacement therebetween, said tip including a rst cylindrical portion of a diameter equal to lthat of the stem, .a conical portion on s-aid first cylindrical portion and of Ia shape substantially corresponding to that of said seat and a second cylindrical portion extending from said conical portion and of a length substantially equal to that of said cylindrical opening whereby the second cylindrical portion is adapted to cleanse said opening of residue materials therein, said tip being of a nylon-like material which is substantially inert with respect to paint and which is substantially more deformable than said rigid ystern whereby said tip `is adapt- `ed to conform to the shape fof said sea-t as .the latter Wears, said tip being of a length substantially greater than its transverse dimension and extending as a solid mass 'and for a substantial length from the rigid stem; means coupled to said needle for yieldably urging said tip into said seat and cylindrical opening and maintaining the tip therein whereby to conform said tip to the shape of said seat, and means to move said needle to Withdraw said tip from said seat .to permit said fluid to pass through said opening.

2. A paint spray device comprising -a metal body provided with an elongated chamber for a paint to be sprayed, said body including a substantially conical seat 4at `an end of said chamber and being provided with a substantially cylindrical opening connected to and concentric with said seat and through which said paint leaves said chamber; a needle extend-ing through said chamber and including an elongated metal stem including an irregular end portion, land a tip on said `stem and engaging said irregular end portion, the engagement between said tip and irregular end portion preventing rotational displacement therebetween, said tip including a first cylindrical portion of a diameter equal to that `of the lstem, la conical portion on said rst cylindrical portion and `of a shape substantially corresponding to that of said seat land a second cylindrical portion extending from said conical portion and substantially corresponding to said cylindrical opening whereby the second cylindrical portion is adapted to cleanse said opening of residue paint therein, :said .tip being of a nylon-like material which is substantially inert with respect 4to paint and which is substantially more deformable than said metal stem whereby said tip is adapted to conform 'to the shape of said seat and opening as said body Wears, said tip being of a length substantially greater than its transverse dimension Iand extending .as a solid mias-s and for a substantial length from the metal stem; means `coupled to said needle for yieldably urging said tip into said seat and cylindrical opening and maintaining lthe tip therein whereby to conform 4said tip to the shape of said seat, and means to move said needle to Withdraw said tip from said seat to permit said paint to pass through said opening; bearing means in said lbody land slidably supporting said metal stem; and means in said body for discharging a pressure medium adjacent said cylindrical opening for atomizing said paint.

References Cited in the ile of this patent UNITED STATES PATENTS 894,558 Wneaton July 28, 1908 1,661,150 Birkenmaier Feb. 28, 1928 1,681,845 Dilley Aug. 2l, 1928 1,775,091 Frank Sept. 9, 1930 1,837,861 Green Dec. 22, 1931 2,214,035 Tracy Sept. 10, 194() 2,343,034 Weber Feb. 29, 1944 2,552,923 Appel May 15, 1951 2,670,239 Ditch Feb. 23, 1954 [2,675,204 Johnson Apr. 13, 1954 2,755,968 Fiant July 24, 1956 2,781,101 Allen Feb. 12, 1957 2,853,097 Davis Sept. 23, 1958 2,914,258 Ruetsch Nov. 24, 1959 2,944,742 Le Btl-anc July 12, 1960 3,022,955 Riddell Feb. 27, 1962 

1. A PAINT SPRAY DEVICE COMPRISING A BODY PROVIDED WITH AN ELONGATED CHAMBER FOR A FLUID TO BE SPRAYED, SAID BODY INCLUDING SUBSTANTIALLY CONICAL SEAT AT AN END OF SAID CHAMBER AND BEING PROVIDED WITH A SUBSTANTIALLY CYLINDRICAL OPENING CONNECTED TO AND CONCENTRIC WITH SAID SEAT AND THROUGH WHICH SAID FLUID LEAVES SAID CHAMBER; A NEEDLE EXTENDING THROUGH SAID CHAMBER AND INCLUDING AN ELONGATED RIGID STEM INCLUDING AN IRREGULAR END PORTION AND A TIP ON SAID STEM AND ENGAGING SAID IRREGULAR END PORTION, THE ENGAGEMENT BETWEEN SAID TIP AND IRREGULAR END PORTION PREVENTING ROTATIONAL DISPLACEMENT THEREBETWEEN, SAID TIP INCLUDING A FIRST CYLINDRICAL PORTION OF A DIAMETER EQUAL TO THAT OF THE STEM, A CONICAL PORTION ON SAID FIRST CYLINDRICAL PORTION AND OF A SHAPE SUBSTANTIALLY CORRESPONDING TO THAT OF SAID SEAT AND A SECOND CYLINDRICAL PORTION EXTENDING FROM SAID CONICAL PORTION AND OF A LENGTH SUBSTANTIALLY EQUAL TO THAT OF SAID CYLINDRICAL OPENING WHEREBY THE SECOND CYLINDRICAL PORTION IS ADAPTED TO CLEANSE SAID OPENING OF RESIDUE MATERIALS THEREIN, SAID TIP BEING OF A NYLON-LIKE MATERIAL WHICH SUBSTANTIALLY INERT WITH RESPECT TO PAINT AND WHICH IS SUBSTANTIALLY MORE DEFORMABLE THAN SAID RIGID STEM WHEREBY SAID TIP IS ADAPTED TO CONFORM TO THE SHAPE OF SAID SEAT AS THE LATTER WEARS, SAID TIP BEING OF A LENGTH SUBSTANITALLY GREATER THAN ITS TRANSVERSE DIMENSION AND EXTENDING AS A SOLID MASS AND FOR A SUBSTANTIAL LENGTH FROM THE RIGID STEM; MEANS COUPLED TO SAID NEEDLE FOR YIELDABLY URGING SAID TIP INTO SAID SEAT AND CYLINDRICAL OPENING AND MAINTAINING THE TIP THEREIN WHEREBY TO CONFORM SAID TIP TO THE SHAPE OF SAID SEAT, AND MEANS TO MOVE SAID NEEDLE TO WITHDRAWN SAID TIP FROM SAID SEAT TO PERMIT SAID FLUID TO PASS THROUGH SAID OPENING. 